But you are missing something. It is the realization that it would be so easy to justify evil that tortures Harry. He is a flawed human character, tempted by the possibility of revenge and by power but even though his way is not perfectly straight, he perseveres to the end and ultimately make the right choice.
Corki, yes, Harry is a flawed charater, good, that is what helps tell a moral story.
But part of being a ‘good’ character is not that one is immune to temptation, or even falls. The hallmark is that when one fails, repents\seeks forgiveness and\or attempts to make ammends.
That’s the key factor in denoting ‘good’ vs ‘evil’. Good does not use evil methods by design, and when it falls for temptation, it expresses regret.
After Harry tortures his opponents, he expresses no remorse, rather, after torturing Carrow, he notes that he got it right that time.
Where exactly in the book does Harry express remorse over torturing Bellatrix or Carrow, where does he attempt to make ammend. Heck, I’d setting if an authority figure such as Dumbledore or McGonagall expressed displeasure in Harry’s actions.
But none of that happened.
Contrast this to Frodo, when the influence of the Ring causes him to lash out at Samwise, what’s the first thing that Frodo does afterward, he aplogizes and tries to make ammends.
Even Boromir does the same after he frightens Frodo and Sam enough to leave the company, in fact he gives his life in reparation.
H.P. has none of this, Harry is a flawed character, so flawed, in fact that he uses evil, shows no remorse and suffers no punishement for the act.
Not exactly what we want to show our kids.